Central nervous system (CNS) angiogenesis, the growth of new blood vessels from preexisting ones, starts during embryonic, persists into early postnatal development in human and rodents. Upon brain injury, such as traumatic brain injury and stroke, endogenous angiogenic attempts occur in response to increased metabolic demands. An increasing amount of animal studies demonstrate that manipulating the endogenous angiogenesis has therapeutic benefits in brain functional recovery. Investigating underlying cellular and molecular mechanisms of CNS angiogenesis during development provides new insights into therapeutic interventions of new blood vessel growth in the adult injured brain. This application aims to study the cellular and molecular mechanisms regulating CNS developmental angiogenesis. Recent data from others and our own laboratory indicate that oligodendroglial lineage cells regulate CNS angiogenesis through hypoxia inducible factor alpha (HIF?) signaling pathway during the normal development of murine brain and spinal cord. However, the underlying molecular mechanisms are still debating. The current accepted concept proposes that oligodendroglial HIF? regulates angiogenesis through activating paracrine Wnt but not VEGF signaling in the vascular endothelial cells. However, the data supporting this popular hypothesis are obtained from in vitro cell and brain slice culture in combination with pharmacological manipulations. Unexpectedly, we found no evidence of Wnt perturbation in the brain and spinal cord of oligodendroglial HIF?-engineered transgenic mice. Instead, we found that VEGF is regulated by oligodendroglial HIF?. In this project, we propose a paradigm-shifting, alternative hypothesis that oligodendroglial HIF? regulates developments angiogenesis through Wnt-independent and VEGF-dependent pathways. To circumvent the non-cell-type-specificity and/or off-target effects of pharmacological compounds and potential ?pathological? activation of Wnt signaling in the in vitro culture system, we propose to employ Cre- LoxP-based genetic approaches to test our hypothesis. In Aim 1, we will conditionally stabilize HIF? function and simultaneously block Wnt secretion from oligodendroglial lineage cell to determine the in vivo involvement of oligodendrocyte-derived Wnt signaling in the angiogenesis in the murine brain and spinal cord. In Aim 2, we will conditionally stabilize HIF? function and simultaneously disrupt VEGF in oligodendroglial lineage cell to define the oligodendrocyte-derived VEGF signaling in CNS angiogenesis. The overall impact of our project is that it will advance our knowledge of cellular and molecular mechanism underlying CNS angiogenesis, and will shift our current understanding of oligodendroglial HIF?-regulated angiogenesis from a Wnt-dependent/VEGF- independent view to a VEGF-dependent/Wnt-independent one, and will provide novel cellular and molecular sights into therapeutic interventions aiming at enhancing CNS angiogenesis.